WO2020125674A1

WO2020125674A1 - Spatial light modulator

Info

Publication number: WO2020125674A1
Application number: PCT/CN2019/126278
Authority: WO
Inventors: 谈顺毅
Original assignee: 上海慧希电子科技有限公司
Priority date: 2018-12-21
Filing date: 2019-12-18
Publication date: 2020-06-25
Also published as: CN109507820A

Abstract

An optical device and an optical system, comprising a one-layered or multi-layered structure; the structure comprises an upper substrate (1), an intermediate medium layer (3), and a lower substrate (2), which are disposed in sequence; the intermediate medium layer (3) is at least one-layered; and a birefringent material (4) is filled between the upper substrate (1) and the intermediate medium layer (3) as well as between the intermediate medium layer (3) and the lower substrate (2). The optical device and the optical system may achieve phase modulation while changing the polarization direction of incident light, while also modulating the intensity and phase of the incident light, thus increasing the response speed of the spatial light modulator to modulation signals.

Description

A spatial light modulator

Technical field

The invention relates to the field of optical devices, in particular, to optical devices and optical systems.

Background technique

Patent document CN101323981A discloses a borate birefringent optical crystal and uses thereof. These crystals are negative uniaxial crystals, and the value of the birefringence in the visible light band is about 0.08-0.15. This series of crystals is easy to cut, grind, polish and store, insoluble in water, not deliquescence, stable in the air, suitable for making optical communication components, such as optical isolators, circulators, beam shifters, optical polarizers and Optical modulator, etc. Especially for making polarizing prisms, phase delay devices and electro-optical modulation devices for various purposes. These devices utilize the refractive index characteristics of the crystal, especially the larger birefringence.

Although this patent document can provide a solution that can apply birefringent materials to optical devices, it does not disclose specific implementations of optical devices.

Summary of the invention

In view of the defects in the prior art, the object of the present invention is to provide an optical device and an optical system.

An optical device provided according to the present invention includes one or more layers of structure;

The structure includes an upper substrate, an intermediate dielectric layer, and a lower substrate arranged in sequence; the intermediate dielectric layer is at least one layer; a birefringent material is filled between the upper substrate and the intermediate dielectric layer, and between the intermediate dielectric layer and the lower substrate.

Preferably, the birefringent material uses liquid crystal.

Preferably, the intermediate dielectric layer is a conductive material or a conductive layer is made on the surface.

Preferably, the intermediate dielectric layer constitutes a polarizer or a film with a polarization function on the surface.

Preferably, the intermediate dielectric layer is multiple layers, and the adjacent intermediate dielectric layer is filled with birefringent material.

Preferably, any one or more of the upper substrate, the lower substrate, and the intermediate dielectric layer have pixel voltage modulation capability and/or overall voltage modulation capability.

Preferably, any one or more surfaces are aligned as follows:

-The surface of the upper substrate facing the birefringent material;

-The surface of the lower substrate facing the birefringent material;

-The surface of the intermediate substrate facing upward to the substrate;

-The surface of the intermediate substrate is down to the substrate.

Preferably, the alignment of at least one of the following surfaces is different from the other surfaces:

-The surface of the upper substrate facing the birefringent material;

-The surface of the lower substrate facing the birefringent material;

-The surface of the intermediate substrate facing upward to the substrate;

-The surface of the intermediate substrate is down to the substrate.

Preferably, the intermediate dielectric layer is a transparent material.

Preferably, the intermediate dielectric layer is ITO and/or TFT glass.

Preferably, the upper substrate and/or the lower substrate are ITO and/or TFT glass.

Preferably, the upper substrate and/or the lower substrate are wafers.

Preferably, the crystal box between the upper substrate and the intermediate dielectric layer and the crystal box between the intermediate dielectric layer and the lower substrate differ in any one or more of the following parameters:

-thickness;

-material;

-Direction of alignment;

-Voltage across the terminal;

-LCD mode.

Preferably, the liquid crystal mode is at least one of ECB, TN, VAN, and FLC.

Preferably, there is a correspondence between pixels on the upper and lower sides of the intermediate dielectric layer.

Preferably, there are multiple intermediate dielectric layers for separating multiple birefringent materials.

An optical device combination provided according to the present invention includes a plurality of the optical devices, and the optical devices are stacked up and down.

Preferably, the sum of the voltages applied on both sides of each layer of birefringent material is zero for a certain period of time.

Preferably, the voltage applied on the substrate and/or the intermediate dielectric layer is an analog signal.

Preferably, the voltage applied on the substrate and/or the intermediate dielectric layer is a digital signal.

An optical system provided according to the present invention includes a control and driving system and the optical device;

Control and drive the system, obtain the data signal, drive the optical device to generate the corresponding light modulation, and synchronize the light source and/or output the synchronization signal.

An optical system provided according to the present invention includes the optical device described above, and further includes a matching device that performs cooperative modulation with the optical device, wherein the matching device includes any one of a light source, a polarizing plate, a PBS, a lens, and a polarizing device One or any multiple devices.

Compared with the prior art, the present invention has the following beneficial effects:

The invention can realize the phase modulation while changing the polarization direction of the incident light. In some application examples, it can also realize the intensity and phase modulation of the incident light.

The invention can improve the response speed of the spatial light modulator to the modulation signal.

Brief description of the drawings

By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, objects, and advantages of the present invention will become more apparent:

1 is a schematic structural diagram of an embodiment of the present invention, showing an upper substrate 1, a lower substrate 2, an intermediate dielectric layer 3, and an intermediate liquid crystal layer 4;

FIG. 2 is an embodiment of the present invention, in which the lower substrate applies voltages V2×1y1-V2×1y5 respectively according to pixels, and the upper substrate and the intermediate dielectric layer respectively apply a whole voltage V1, Vcom;

FIG. 3 is another embodiment of the present invention, wherein the upper and lower substrates apply voltages respectively according to pixels, and the middle dielectric layer applies a whole voltage; the upper substrate applies voltages according to pixels V1×1y1-V1×1y5;

4 is an embodiment of the present invention, wherein the lower substrate is a transmissive type (for example, TFT glass);

FIG. 5 is an embodiment of the present invention, wherein the lower substrate is reflective (for example, a silicon-based wafer);

6 is an embodiment of the present invention, in which the upper layer material between the upper substrate and the intermediate dielectric layer rotates the polarization direction of incident light by 45°, and the lower layer material between the lower substrate and the intermediate dielectric layer realizes phase modulation of the incident light;

FIG. 7 is an embodiment of the present invention, in which the upper layer material between the upper substrate and the intermediate dielectric layer modulates the polarization direction of incident light according to pixel points (intensity modulation can be achieved after adding a polarizer), and the lower substrate and the intermediate dielectric The underlying materials between the layers realize phase modulation of the incident light;

8 is a comparison diagram of the alignment directions of the upper and lower substrates and the surface of the intermediate dielectric layer in an embodiment of the present invention.

Preferred embodiments of the invention

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that, those of ordinary skill in the art can make several changes and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

An optical device according to the present invention includes one or more layers of structures; the structure includes: an upper substrate, a lower substrate, and at least one intermediate dielectric layer; between the upper substrate and the intermediate dielectric layer (multilayer structure In this case, a birefringent medium may be filled between the intermediate dielectric layer and the intermediate dielectric layer), and between the intermediate dielectric layer and the lower substrate. Each layer is separated by a conductive intermediate dielectric layer.

A voltage is applied to at least one of the upper substrate and the lower substrate (voltage is applied according to pixels, and the voltage at each point may be different, for example, an LCoS wafer is used as a substrate, or a substrate of an LCD screen, etc.), and the intermediate dielectric layer is on at least one surface Apply voltage (total application). The filled birefringent material may be a liquid crystal material, the thickness of the crystal layers located on the upper and lower sides of the intermediate dielectric layer may be the same or different, and the modes of the liquid crystals located on the upper and lower sides of the intermediate dielectric layer may be the same or different. The upper and lower substrates can be TFT/ITO glass or silicon-based wafers, the intermediate dielectric layer can be TFT or ITO glass, and the surfaces of the upper and lower substrates facing the birefringent material and the two surfaces of the intermediate dielectric are aligned Processing, for example, using a rubbing process to align, the specific method is to rub the above surface in a certain direction using a corresponding felt (which can be installed on a roller), so that the liquid crystal molecules can be filled into a set distribution according to the direction of alignment after filling. At least one of the four surfaces of the upper substrate and the lower substrate facing the surface of the birefringent material and the two surfaces of the intermediate medium has a different alignment direction from the other surfaces. Therefore, the function of simultaneously changing the polarization direction of the incident light and modulating the phase of the incident light is realized. It is also possible to make the alignment directions of the four surfaces all the same, then at this time compared to the single-layer device that reaches the same modulation range (the thickness of the single-layer liquid crystal will be the sum of the thicknesses of the two layers of the double-layer device in the present invention, and The reaction speed of the material is directly related to its thickness) The refresh rate of the device will be several times that of a single-layer device, so as to improve the refresh rate.

In addition, the optical system composed of this device also includes a control and drive system and other optical elements. The control and drive system is mainly composed of electronic devices, which control to generate data signals and drive the device to generate corresponding light modulations. Synchronize the light source. Other optical devices may include light sources (such as LD, LED, etc.), polarizers or polarizing prisms, lenses, lens groups, etc. Polarizers or polarizing prisms are used to combine the light beams and/or to filter unwanted light, and lenses and lenses are used to modulate the light beams again (eg, enlarge/reduce the image, etc.).

Example 1

In one embodiment, the lower substrate uses a silicon-based liquid crystal wafer with a resolution of 1920x1080, and both the intermediate dielectric layer and the upper substrate use ITO glass. The liquid crystal is selected as the upper layer liquid crystal adopting TN mode packaging, and the lower layer adopting ECB mode packaging. One possible alignment selection is that the lower substrate surface and the intermediate dielectric layer surface are aligned at 45° to one side of the device, while the upper substrate surface is aligned parallel or perpendicular to one side of the device. The distance between the upper substrate and the ITO glass is 1um (that is, the upper liquid crystal layer is 1um thick), and the distance between the ITO glass and the lower substrate is 2.5um (that is, the lower liquid crystal is 2.5um thick).

The light source (pixel) uses an OLED display panel, and a polarizing prism is added to the light path. The incident light (including image information) emitted by the light source can first pass through a polarizer to make its polarization direction into the P direction when it enters the polarizing prism. After being turned 90° by the polarizing prism, it is incident on the above spatial light modulator. Since the alignment direction of the upper substrate of the device is 45° different from that of the middle ITO glass, the polarization direction of the incident light will be rotated by 45° after passing through the upper liquid crystal, and the lower substrate It is a silicon-based liquid crystal wafer. The surface can be reflected back by the CMP process (it can also be coated with an anti-reflection film with a set wavelength or wavelength range), and is modulated by the control system to be able to be on different pixels. Apply different voltages to the liquid crystal, so that the phase modulation of the incident light at different points is different. When the light returns from the lower layer and enters the upper layer again, the polarization direction is rotated again by 45°. When it exits from the upper layer to the polarizing prism, its polarization The direction has changed to S direction, which can be transmitted through the polarizing prism, amplified by the subsequent optical system, or directly viewed by the viewer.

In the above embodiment, the light source can be replaced with a traditional silicon-based liquid crystal device. After the LD or LED illuminates its surface through a polarizing prism, the polarization direction of the image light is changed by 90° and returns to the polarizing prism. The image light is introduced into the spatial light modulator for modulation After modulation, the polarization direction is changed again by 90° and output through the same polarization prism. The advantage of this is that a polarizing prism is used in the system, which has a compact structure and a small volume.

In the above example, a lens system can also be added to the light source to modulate the light emitted by the light source by collimating, expanding, and homogenizing.

In addition, when the control system controls the change of the substrate voltage, it is often necessary to apply a voltage to the intermediate dielectric layer to achieve the voltage difference across the lower liquid crystal, and due to the DC balance requirement (DC BALANCE) of the liquid crystal modulation, the voltage of the intermediate dielectric layer is also There is a periodic change, for example, the previous cycle is 6V, the next cycle is 0V, so the cycle, you can also apply the same voltage to the upper surface substrate, for example, the previous cycle is 6V, the next cycle is 0V so as not to make the liquid crystal Deflection destroys the modulation of the polarization direction, and at the same time keeps the sum of the pressure difference between the two ends at zero for a certain period of time, so that no damage will occur.

In the above example, the upper substrate can also be replaced with a TFT glass substrate with pixel voltage modulation capability, so as to realize the modulation of the polarization of each pixel, so that the combination of polarizing prism or polarizer can achieve the intensity and phase of the pixel at the same time. modulation. In this case, the light source only needs to realize illumination without providing image information (intensity information). For example, a common LD laser can be used. When the laser is incident, the polarization direction is consistent with the alignment direction of the upper substrate, and each pixel on the upper substrate The points are controlled by the control driving system to apply voltages respectively. When entering the intermediate dielectric layer from the upper substrate, the polarization direction of each pixel point is changed by the voltage modulation, and the amount of change is between 0 and 45°. The polarization directions of all pixels can be equivalently decomposed into a combination of the direction consistent with the alignment direction of the lower substrate and the direction perpendicular to the alignment direction of the lower substrate. Since the long axis direction of the liquid crystal material of the lower layer coincides with the alignment, all pixels propagate Of the light reaching the lower layer, only the energy of the polarized part consistent with the alignment direction of the lower layer will be correctly modulated by the lower liquid crystal (you can also use a polarizer to make an intermediate dielectric layer, or make a coating with polarizing filter properties on the intermediate dielectric layer. The light in the polarization direction that is correctly modulated by the lower layer liquid crystal is filtered out). After it is reflected back, it passes through the upper substrate again, and the polarization direction is changed again. After passing through the subsequent polarizer or polarizing prism (it can be directly made on the upper substrate) (On the surface, or the upper substrate is made of materials with similar characteristics), it can filter out unnecessary energy, thereby simultaneously realizing the intensity and phase modulation of light.

In the above embodiment, the upper layer may also be designed as a phase modulation (layer between the upper substrate and the intermediate dielectric layer), and the lower layer (layer between the lower substrate and the intermediate dielectric layer) may be designed as the intensity modulation, which is similar to the above example. This can be achieved by simply changing the alignment direction and the thickness of the crystal layer. For example, the alignment directions of the upper substrate and the opposite intermediate dielectric layer are the same, the alignment directions of the lower substrate and the facing intermediate dielectric layer are different by 45°, and the alignment directions of the upper and lower surfaces of the intermediate substrate are the same or different by a certain angle.

In the above embodiments, the pixel size (pixel pitch) of the upper substrate and the lower substrate may be the same, and the pixel positions correspond one-to-one in space. Of course, in most cases, the size of pixels produced on a glass substrate (such as a liquid crystal panel) is often larger than the size of pixels on a silicon-based wafer, so the above sizes can also be different. For example, one pixel on the upper substrate is equal to the lower substrate 9 (3×3 ) Pixel size. At this time, when calculating the input data, it is necessary to consider the situation that the intensity or phase of each 9 pixels will be basically the same during the phase modulation of the lower layer, and the error caused by the intensity or phase of some pixels must be appropriately eliminated through the adjustment of the algorithm.

Example 2

In Embodiment 2, both the upper substrate and the lower substrate are made of transparent materials. The upper substrate and the lower substrate are TFT substrates with pixel voltage modulation capability. The alignment direction of the upper substrate and the surface of the dielectric layer facing it is about 90° different. The alignment direction of the substrate and the surface of the corresponding dielectric layer is consistent, and it is consistent with the alignment direction of one surface of the upper substrate or the surface of the dielectric layer corresponding to the upper substrate, and the polarization direction of the light emitted by the light source after passing through the upper substrate is changed and changed The amount is determined by the input signal of each pixel. The same as the above example is that the polarization direction of all pixels can be equivalently decomposed into a direction that is consistent with the alignment direction of the lower substrate and a direction perpendicular to the alignment direction of the lower substrate, because the long axis direction of the liquid crystal material of the lower layer is consistent with the alignment , So all the light propagating from the pixels to the lower layer will only have the energy of the polarized part in the same direction as the alignment of the lower layer will be correctly modulated by the lower liquid crystal. The difference from the above example is that the lower substrate is also transparent in this example, and the modulated light will be Through the substrate, after adding a polarizer (or the intermediate dielectric layer is made to have the characteristics of a polarizer) or a polarizing prism, unnecessary light energy can be filtered out, and the light field with the required intensity and phase can be modulated distributed.

Example 3

Another application is to reduce the thickness of a single layer of material by laminating multiple layers of birefringent materials (thickness and response time are generally in a square relationship, the smaller the thickness, the faster the response speed of the material), so as to achieve the same phase and /Or within the intensity modulation range, improve the response time of the device itself. For example, in Embodiment 3, the optical device includes a multi-layer structure (including three layers of birefringent materials), the lower substrate uses a silicon-based liquid crystal wafer, and a conductive dielectric layer is located at a distance of 1.8um from the wafer, and the conductive dielectric layer has two surfaces The alignment direction is the same as that of the lower layer substrate, the liquid crystal material is filled between the two layers, the conductive medium layer is at least 1.8um at a transparent intermediate layer substrate, and electrodes are made on it, which can perform voltage modulation for each pixel separately. The alignment direction of the side facing the conductive medium layer is consistent with the conductive medium layer, and liquid crystal material is filled between the two layers. A thin film with a polarization selection function can also be plated on the intermediate layer substrate, so as to filter the energy in unnecessary polarization directions. The 1um position on the middle layer substrate is the upper layer substrate. The alignment direction of the surface of the middle layer substrate facing the upper layer substrate is 45° different from that of the upper layer substrate, which can change the polarization direction of incident light. The advantage of the above example is that the response time of the device can be accelerated by the simultaneous modulation of the middle layer and the lower layer. In the above example, there may be no upper layer, but only two or more layers are used to speed up the reaction time of the device.

In addition, the alignment directions of the upper and lower layers in all the above embodiments can also be interchanged, and the system can be changed accordingly.

In the description of this application, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", The orientation or positional relationship indicated by "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, only for the convenience of describing the application and simplifying the description, rather than indicating or implying the device referred to Or the element must have a set orientation, be constructed and operated in the set orientation, and therefore cannot be understood as a limitation of the present application.

The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above-described set embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the case of no conflict, the embodiments of the present application and the features in the embodiments can be arbitrarily combined with each other.

Claims

An optical device, characterized in that it includes one or more layers of structure;

The structure includes an upper substrate, an intermediate dielectric layer, and a lower substrate arranged in sequence; the intermediate dielectric layer is at least one layer; a birefringent material is filled between the upper substrate and the intermediate dielectric layer, and between the intermediate dielectric layer and the lower substrate.
The optical device according to claim 1, wherein the birefringent material uses liquid crystal.
The optical device according to claim 1, wherein the intermediate dielectric layer is a conductive material or a conductive layer is made on the surface.
The optical device according to claim 1, wherein the intermediate dielectric layer constitutes a polarizing plate or a film having a polarizing function on the surface.
The optical device according to claim 1, wherein the intermediate dielectric layer is a multi-layer, and the adjacent intermediate dielectric layer is filled with a birefringent material.
The optical device according to claim 1, wherein any one or more of the upper substrate, the lower substrate, and the intermediate dielectric layer have pixel voltage modulation capability and/or overall voltage modulation capability.
The optical device according to claim 1, wherein any one or more of the following surfaces are aligned:

-The surface of the upper substrate facing the birefringent material;

-The surface of the lower substrate facing the birefringent material;

-The surface of the intermediate substrate facing upward to the substrate;

-The surface of the intermediate substrate is down to the substrate.
The optical device according to claim 7, characterized in that the alignment of at least one of the following surfaces is different from the other surfaces:

-The surface of the upper substrate facing the birefringent material;

-The surface of the lower substrate facing the birefringent material;

-The surface of the intermediate substrate facing upward to the substrate;

-The surface of the intermediate substrate is down to the substrate.
The optical device according to claim 1, wherein the intermediate dielectric layer is a transparent material.
The optical device according to claim 9, wherein the intermediate dielectric layer is ITO and/or TFT glass.
The optical device according to claim 1, wherein the upper substrate and/or the lower substrate are ITO and/or TFT glass.
The optical device according to claim 1, wherein the upper substrate and/or the lower substrate are wafers.
The optical device according to claim 2, wherein the crystal box between the upper substrate and the intermediate dielectric layer and the crystal box between the intermediate dielectric layer and the lower substrate are different in any one or more of the following parameters :

-thickness;

-material;

-Direction of alignment;

-Voltage across the terminal;

-LCD mode.
The optical device according to claim 13, wherein the liquid crystal mode is at least one of ECB, TN, VAN, and FLC.
The optical device according to claim 1, wherein the pixel points on the upper and lower sides of the intermediate dielectric layer have a corresponding relationship.
The optical device according to claim 1, characterized in that it has multiple intermediate dielectric layers for separating multiple birefringent materials.
An optical device combination is characterized by comprising a plurality of optical devices according to claim 1, the optical devices being stacked up and down.
The optical device according to claim 1, characterized in that the sum of the voltages applied to both sides of each layer of birefringent material within a certain period of time is zero.
The optical device according to claim 1, wherein the voltage applied on the substrate and/or the intermediate dielectric layer is an analog signal.
The optical device according to claim 1, wherein the voltage applied on the substrate and/or the intermediate dielectric layer is a digital signal.
An optical system, comprising a control and drive system, the optical device according to any one of claims 1 to 16 or any one of claims 18 to 20;

Control and drive the system, obtain the data signal, drive the optical device to generate the corresponding light modulation, and synchronize the light source and/or output the synchronization signal.
An optical system, including the optical device according to any one of claims 1 to 16 or any one of claims 18 to 20, further comprising a cooperating device that performs cooperating modulation with the optical device, wherein The matching device includes any one or more of a light source, a polarizer, a PBS, a lens, and an optically active device.